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happily supplied by the discovery of the numerous star-form planets, occupying the very space where the unexplained vacancy presented a strong objection to his theory.

According to Bode, the distances of the planets may be expressed nearly as follows: the Earth's distance from the Sun being 10.

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Comparing these values with the actual mean distances of the planets from the Sun, 7 cannot but remark the near agreement, and can scarcely hesitate to pronounce that the respective distances of the planets from the Sun, were assigned according to a law, although we are entirely ignorant of the exact law, and of the reason for that law. Brinkley's Elements, p. 89.

471. The Asteroids are much smaller in size than the older planets-they all revolve at nearly the same distances from the Sun, and perform their revolutions in nearly the same periods their orbits are much more eccentric, and have a much greater incli sation to the ecliptic-and what is altogether singular, except iu the case of comets-some of their orbits cross each other; so that here is even a possibility that two of these bodies may, some time, in the course of their revolutions, come into collision.

The orbit of Vesta is so eccentric, that she is sometimes farther from the Sun than either Ceres, Pallas, or Juno, although her mean distance is many millions of miles less than theirs. The orbit of Vesta crosses the orbits of several other asteroids, in two opposite points.

The student should here refer to the Figures, Map I. of the Atlas, and verify such of these particulars as are there represented. It would be well for the teacher require him to observe particularly the positions of their orbits, and to state their different degrees of inclination to the plane of the ecliptic.

472. From these and other circumstances, many eminent astronomers are of opinion, that these telescopic planets are the fragments of a large celestial body which once revolved between Mars and Jupiter, and which burst asunder by some tremendous convulsion, or some external violence. The discovery of Ceres, by Piazzi, on the first day of the present century, drew the attention of all the astronomers of the age to that region of the sky, and every inch of it was minutely explor ed The consequence was, that in the year following, Dr. Olbers, of Bremen, announced to the world the discovery of Pallas, situated not many degrees from Ceres, and very much resembling it in size.

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How substantially jusfied? 471. Size of the asteroids? Distance from the Sun? Periodic time? Forms of their orbits? Position with respect to the elipti other singularity in their orbits? What remarkable facts respecting the orbit o. Vesta! 479. What conclusion has been drawr from these facts? Progress of discovery?

473. From this discovery, Dr. Olbers first conceived the iden that these bodies might be the fragments of a former world; and if so, that other portions of it might be found either in the same neighborhood, or else, having diverged from the same point, "they ought to have two common points of reunion, or two nodes in opposite regions of the heavens through which all the planetary fragments must sooner or later pass."

474. One of these nodes he found to be in the constellation Virgo, and the opposite one in the Whale; and it is a renaikable coincidence that it was in the neighborhood of the latter constellation that Mr. Harding discovered the planet Juno. In order, therefore, to detect the remaining fragments, if any existed, Dr. Olbers examined, three times every year, all the small stars in Virgo and the Whale; and it was actually in the constellation Virgo, that he discovered the planet Vesta. Since that time, very many additional asteroids have been discovered, and it is not unlikely that still additional fragments of a similar description will hereafter be discovered.

Dr. Brewster attributes the fall of meteoric stones to the smaller fragments of these bodies happening to come within the sphere of the Earth's attraction.

Meteoric stones, or what are generally termed aerolites, are stones which sometimes fall from the upper regions of the atmosphere upon the Earth. The substance of which they are composed, is, for the most part, metallic; but the ore of which it consists is not to be found in the same constituent proportions in any kr own substance upon the Earth. Their fall is generally preceded by a luminous appearance, a hissing noise, and a loud explosion; and when found immediately after their descent, they are always hot, and usually covered with a black crust, indicating a state of exterior fusion.

Their size varies from that of small fragments of inconsiderable weight to that of the most ponderous masses. They have been found to weigh from 300 pounds to several tons; and they have descended to the earth with a force sufficient to bury them many feet under the surface.

Some have supposed that they are projected from volcanoes in the Moon; others that they proceed from volcanoes on the Earth; while others imagine that they are generated in the regions of the atmosphere; but the truth probably is not yet ascertained. Ir some instances, these stones have penetrated through the roofs of houses, and proved destructive to the inhabitants.

If we carefully compute the force of gravity in the Moon, we shall find that if a body were projected from her surface with a momentum that would cause it to move at the rate of 8200 feet in the first second of time, and in the direction of a line joining the centers of the Earth and Moon, it would not fall again to the surface of the Moon; but would become a satellite to the Earth. Such an impulse might, ir deed, cause it, even after many revolutions, to fall to the earth. The fall, therefore, of these stones, from the air, may be accounted for in this manner.

Mr. Harte calculates, that even a velocity of 6000 feet in a second, would be sufficient to carry a body projected from the surface of the Moon beyond the power of her attraction. If so, a projectile force three times greater than that of a cannon, would carry a a body from the Moon, beyond the point of equal attraction, and cause it to reach the Earth. A force equal to this is often exerted by our volcanoes, and by subterrar.ean steain. Hecce, there is no impossibility in the supposition of their coming from the Moon.

478. Theory o. Dr. Olbers? 474. Where did he find these nodes? What remarkable coincidence? Dr. Olbers' efforts? Discoveries since? Dr. Brewster's idea respecting meteoric stones? What are meteoric stones? Circumstances of their fall? Size and weight? Supposed origin? Could they have fallen from the Moon? What computations i

475. Vesta is the only asteroid that can be seen with the m ked eye.

476. The largest of the asteroids is probably about 220 Lilea n diameter; the smallest is less than 20 miles.

477. The following table comprises their names, &c.:

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6. Hebe..

7. Iris..

8 Flora.

9. Metis..

1. Ceres..

2. Pallas.

3. Junc.

4. Vesta.

252,959,381 1,681 Jan. 1, 1801
253,221,523 1,684 March 28, 1802
243,971,812 1,592 Sept. 1,
215,893,659 1,325 March 29, 1807

221,797,635 1,380 | July 1, 218,173,325 1,346 Aug. 13, 201.273,127 1,193 Oct. 18, 218,211,451 1,347 April 25, 0. Hygeia... 238,110,375 2,043 April 12, 11. Parthenope.. 224.181.315 1,402 May 13, 12. Victoria..... 213.597.600 1,302 Sept. 13, 13. Egeria... 235,581,675 1,511 Nov. 2, 14. Irene.. 15. Eunomia.. 16. Psyche.. 17. Thetis... 18. Melpomene.. 19. Fortuna....... 20. Massilia..

236,441.215 1,519 May 20, 241,712,103 1,570 July 29, 267,311.899 1,826 March 17, 226,156,795 1,421 April 17, 209,891.225 1.270 June 24, 223,195,117 1.393 Aug. 22, 220,311,715 1,366 Sept. 19, 222,673,235 1,388 Nov. 15, 265,988,156 1,814 Nov. 18, 240,194,177 1,555 Dec. 15, 287,371,205 2,035 April 5, 219,507,125 1,359 April 6, 242,844,895 1,581 May 5, 214,561,317 1,313 Nov. 8, 28. Bellona. 254,036,415 1,692 March 1, 29. Amphitrite.. 233,509,171 1,491 March 1, 30. Urania 216,275,879 1,329 July 22, 31. Euphrosyne. 288,251.117 2,015 Sept. 1, 32. Pomona.. 236,556,455 1,520 Oct. 26,

1. Lutetia.. 22. Calliope. 23. Thalia... 24. Themis.. 25. Phocæa.. 26. Proserpine.. 27. Euterpe.

89. Lætitia.

40 Harmonia.
41 Daphne.
42 Isis.

33. Polyhymnia. 261,863,473 1,770 Oct. 28,
34. Circe.... 245,615,324 1,608 April 15,
35. Leucothea. 274,897,315 1,904 April 19,
36. Atalanta.. 251,079,425 1,662 Oct. 5,
37. Fides.. 241,499,127 1,568 Oct. 5,
28. Leda.
250,531,915 1,657 Jan. 12,
252,994,125 1,681 Feb. 8,
207.295,315 1,247 March
253,183,175 1,683 May 23,
223,095,367 1,392 May 23,
201,445.216 1,195 April 15,
221,441.119 1,377 May 27,
248,801,071 1,610 June 27,
230,994,315 1,467 Aug. 16,
263,432,471 1.786 Sept. 15,
284,293,510 2,003 Sept. 19,
281,833,015 1,977 Sept. 19,
242,203,713 1,575 Oct. 4,

43 Ariadne. 44 Nysa.. 43 Eugenia... 46 Hestia.. 47. Aglaia... 48. Doris 49. Pales..

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51. Nemausa... 216.296,571 1,329 Jan. 22,
263,431,110 1,994 Feb. 4,
239,521,473 1,549 April 4,
247.986.795 1,632 Sept. 11,
252,262,491 1,674 Sept. 11,
237.347,157 1.528 Sept. 9.
288,602,121 2,048 Sept. 22,
246,889,315 1.621 March 24, 1860
248,059,106 1.632 Sept. 12,
218,796,250 1,352 Sept. 15,
272,898,017 1.883 Sept. 19,
286,145,013 2,022 Oct. 10,
218,971,905 1,354 Feb. 10,
245.117,875 1,603 March 2,
1312,737,913 2,311 March 4,
242,404,596 1,577 April 9,
221,419,105 1,377 April 17,
254,212,089 1,693 April 20,
69. Hesperia... 271,702,518 1,871 April 29,
70. Panopea.... 238,931,095 1,513 May 5,

33. Ausonia... 64. Angelina.. 65. Cybele.

66. Maia..

67. Asia..

68. Leto..

71. Feronia..

72. Niobe.

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207,187,414 1,246 May 29, 251,934,138 1,671 Aug. 13, 243,806,171 1,590 April 7, 253,964,819 1,691 Aug. 29, 244,101,375 1,593 Sept. 22, 309,736,915 2,277 Oct. 21, 77. Frigga. 244,294,717 1,595 Nov. 12, 78. Diana.. 239,798,051 1,551 March 15, 79. Eurynome.. 223,379,507 1,395 Sept. 14, 80. Sappho.. 209,950.819 1,271 May 2, 81. Terpsichore 261,151,257 1,763 Sept. 30, 82. Alcmene. 252,372.105 1,675 Nov. 27, 222,061,135 1,383 April 26, 216,457,309 1,331 Aug. 25, 242,618,417 1,573 Sept. 19, 282,591,045 1,985 Jan. 4, 319,337,561 2,384 May 17, 253,278,071 1.684 June 15, 233,131,645 1,486 Aug. 5, 285,155,396 2,011 Oct. 1, 237,333,994 1,528 Nov. 24, 291,844,560 2,081 July 26, 251,981,082 1.672 Aug. 24, 286,175,900 2,062 Sept. 6, 95. Arethusa... 280,598,670 1,960 Nov. 10, 279,227,220 1,949 Feb. 17, 244,023,675 1,591 Feb. 17, 245,398,120 1,506 April 18, 251,375,126 1,660 May 28, 273,649.992 1,891 July 11, 235,249,390 1,507 Ang 15, 243,478.090 1,588 Aug 24, 247,043,860 1,621 | Sept. 7, 290,747,415 2,069 Sept. 13, 217,603,400 1.340 Sept. 16, 292,667,430 2,091 Oct. 10, 325,758,300 2,454 291,935,989 2,084

90. Antiope... 91. Egina.. 92. Undina

93. Minerva..

94. Aurora..

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Since the discovery of Felicitas, nineteen other asteroids have been announ:A. Alaki g the whole Lumber, up to 1873, one hundred and twenty-eight.

98. Ianthe.. 99. Dikë.. 100. Hecate.. 101. Helena.. 102, Miriam.. 103. Hera... 104. Clymene....

CHAPTER VII.

PRIMARY PLANETS-JUPITER AN) SATURN.

47. JUPITER is the largest of all the planets belonging to the Biar system. It may be readily distinguished from the fixed tars, by its peculiar splendor and magnitude; appearing to the aked eye almost as resplendent as Venus, although it is more than seven times her distance from the Sun.

When his right ascension is less than that of the Sun, he is our morning star, and appears in the eastern hemisphere before the Sun rises; when greater, he is our evening star, and lingers in the western hemisphere after the Sun sets.

Nothing can be easier than to trace Jupiter among the constellations of the zodiac; for in whatever constellation he is seen to-day, one year hence he will be seen equally advanced in the next constellation; two years hence, in the next; three years hence, in the next, and so on; being just a year, at a mean rate, in passing over one constellation.

The exact mean motion of Jupiter in its orbit, is about one-twelfth of a degree in a day; which amounts to only 30° 20' 32" in a year.

For 12 years to come, he will, at a mean rate, pass through the constellations of the zodiac, as follows:

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479. Jupiter is the next planet in the solar system above the asteroids, and performs his annual revolution around the Sun in nearly 12 of our years, at the mean distance of 475,000,000 of miles; moving in his orbit at the rate of 29,000 miles an hour.

The exact period of Jupiter's sidereal revolution is 11 years, 10 months, 17 days. 14 hours, 21 minutes, 25 seconds. His exact mean distance from the Sun is 475.693,000 miles; consequently, the exact rate of his inotion in his orbit is 28,744 miles per hour 480. He revolves on an axis, which is nearly perpendicular to the plane of his orbit, in 9 hours, 55 minutes, and 50 seconds; 30 that his year contains 10,471 days and nights; each about o hours long.

His form is that of an oblate spheroid, whose polar diameter

478. Comparative size of Jupiter? How distinguished from the fixed stars? When morning star, &c.? Is he easily traced? 479. His position in the system? His poi rate time? Distance from the Sun? Rate of motion? 480. Time of diurna. revciu hon? Position of axis? Length of his days? Number in his year? His form Cator fais oblateness? Difference of equatorial and pelar diameters? The Earth?

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